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Probotix FireBall V90 CNC Robot 


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Probotix FireBall V90 CNC Robot 

Written By: Sean Michael Ragan 


Acetone (1) 

Hex/ Allen wrenchs (2) 

Phillips head screwdriver (2) 

Ra g (1 ) 

Screwdriver (1) 

Wrench (2) 


Although the V90 is an entry-level machine, it's decidedly not a toy. The way it functions is 
complicated — a platform carries the tool holder; a larger gantry moves the tool back and 
forth; the frame positions the gantry; and it's all driven by a motor turning the screw 
interposed between two shafts. Indeed, this three-axis Cartesian robot is probably the most 
complex machine I've ever built, and I had expected it to be correspondingly difficult to 
assemble; however, quite the contrary — it's easier than many common bike repairs. A 
thriving community actively updates the online build guide, and all the materials were very 
helpful during my own build. 

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Probotix FireBall V90 CNC Robot 

Step 1 — Clean the rails 


• The bearings in your V90 
are made of Qilite , a 
microporous metal vacuum- 
impregnated with lubricant. The 
centerless ground shafts ("rails") in 
your kit ship with a waxy, 
protective coating, that must be 
removed before they are installed 
in these bearings, otherwise the 
waxy material will clog the oilite 
pores and ruin the bearings. Do not 
install the shafts in the bearings 
without cleaning them first! 

• Moisten a soft cloth with acetone 
and wipe down the shafts until the 
surface no longer feels waxy. 

• Be sure to clean all four 
rails. There are two smaller, 
0.625" diameter rails for the short 
horizontal axis, and two larger 
0.750" diameter rails for the long 
horizontal axis. 

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Probotix FireBall V90 CNC Robot 

Step 2 — Insert the rails into the bearings 

• Insert each of the longer, 0.750" diameter shafts into one of the two gantry slides, as 

• Insert both of the shorter, 0.625" diameter shafts into the Z-axis assembly. 

Step 3 — Assemble the gantry 

• Mount two of the smaller white, cup-shaped rail end bushings to each of the two gantry 
uprights, as shown, by inserting the threaded bolts on the bushings into the corresponding 
holes in the uprights. Secure each with a single nut, just finger-tight, for now. 

• Slip the rail end bushings over the ends of the two gantry rails. 

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Probotix FireBall V90 CNC Robot 

Step 4 — Install gantry tension rods 

• Slip the four shorter lengths of threaded rod ("tension rods") into the four holes in each of 
the uprights, as shown. 

• The back (silver) and bottom (black) gantry frame members each have two grooves to 
receive the tension rods. Slip both frame members in place over the rods, as shown. 

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Probotix FireBall V90 CNC Robot 

Step 5 — Install and tighten gantry bolts 

• Add a flat washer and a hex nut over each exposed end of each tension rod. Tighten the 
nuts down finger tight. 

• Set the gantry upright on the bench, as shown, and tighten each tension rod, with a wrench 
on each end. Do not overtighten! One turn past finger-tight is plenty. 

• Adjust the tension on the rods as necessary to square up the gantry. A good test for 
squareness is that the Z-axis assembly slides smoothly on the rails, without binding. 

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Probotix FireBall V90 CNC Robot 

Step 6 — Install upper lead screw 

• Choose the side of the gantry on which you want to mount the short-horizontal-axis 
stepper motor. Both sides have motor mounting holes, and the choice is only one of 
convenience. Think about clearances and cable pathways in the place you're eventually 
going to be using the robot. 

• Insert the end of the smaller lead screw without the brass coupling through the hole in the 
gantry upright on which you plan to mount the motor. 

• Once the tip of the lead screw is between the gantry uprights, slip a bearing assembly, a 
nylon washer, and a shaft collar onto it, in that order. Note the correct orientation of the 
bearing assembly, with the narrower end closest to the gantry upright. 

• Carefully thread the lead screw through the anti-backlash nut in the Z-axis assembly. The 
anti-backlash nut ships with a small cardboard tube inside it, which will be pushed out as 
you thread in the lead screw. 

• NOTE: Do not attempt to remove the cardboard tube in any other way. Likewise, do 
not remove the lead screw from the anti-backlash nut once it is threaded through. 
Without either the tube or the lead screw in place inside the anti-backlash nut, it will fall 
apart, and can be quite tricky to get back together. See this document for more info. 

• Once the lead screw is through the anti-backlash nut, slip a shaft collar, a nylon washer, 
and the other bearing assembly onto its exposed end. Push the lead screw in, sliding the 
Z-axis assembly with it, until the bearing assembly is secure in the far gantry upright. 

• Adjust the lead screw such that about 3/4" of the brass coupling is exposed outside the 
gantry. Position the shaft collars close up against the washers and bearings at each end of 
the lead screw, and use a 7/64" Allen wrench to tighten them down. 


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Probotix FireBall V90 CNC Robot 

Step 7 — Install lower drive nut 

• The lower drive nut is a second anti-backlash nut that comes pre-installed in a 
bracket with two mounting holes, like the blue one shown here. To install it, you will 
need two machine screws, six flat washers, and two matching hex nuts. 

• Pass the two machine screws through the mounting holes in the gantry floor, from the top 

• Slip two flat washers over each exposed screw end. These serve as spacers between the 
gantry floor and the lower drive nut assembly, and can be removed (or supplemented) 
later, if necessary, to adjust its height. 

• Slip the lower drive nut assembly over the exposed screw ends and doubled flat washers. 

• Add an additional flat washer, and a hex nut, to each exposed screw end. Tighten the hex 
nuts to secure the lower drive nut assembly. As always, be careful not to overtighten. 

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Probotix FireBall V90 CNC Robot 

Step 8 — Install large rail end bushings 

• NOTE: My V90 arrived with the table support bars pre-installed on the base ends. If 
yours did not, don't fret: it isn't complicated. Refer to the Probotix assembly guide 
for details. 

• Each base end gets two of the larger, white, cup-shaped rail-end bushings. The white 
"cups" go on the same side of the base ends as the circular grooves. 

• Secure each rail-end bushing with a flat washer and a hex nut on the ungrooved side of 
each base end. Tighten the nuts down one turn past finger-tight. 

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Probotix FireBall V90 CNC Robot 

Step 9 — Assemble the base 

• At least one, and possibly both, of the base ends in your V90 kit will have four small 
motor mounting holes, arranged in a square, in the center. If you have a base-end 
without motor mounting holes, start with it. If both your base ends have motor mounting 
holes, it doesn't matter which you start with. 

• Use magazines, phonebooks, rags, or other padding to cushion one base end flat against 
your work surface, with the grooves and rail-end bushings facing up. Try to get it level, and 
make sure it doesn't rock too easily on the bolt heads. 

• Slip the large 0.750" diameter guide rails, with attached gantry slides, into the upright rail- 
end bushings. Note the correct orientation of the gantry slides: With their flats rotated 
away from the table support bars, the wider part of each flat should be oriented toward the 
inside of the frame. 

• Slip the plastic pipe sections-two large and two small-into the corresponding circular 
grooves on the base end. This is where it helps for things to be level. 

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Probotix FireBall V90 CNC Robot 

Step 10 — Install tension rods 

• Slip a flat washer onto the end of each of four long threaded tension rods, and follow it up 
with a cap nut. Tighten each cap nut all the way down with your fingers. 

• Lift the other base end into place over the upright rails and pipe sections, mating the two 
free rail ends with the rail-end bushings and the four free pipe ends with the circular 

• The tension rods run inside the pipe sections. Lower one into each of the four holes in the 
upper base end. The flat washers and cap nuts will keep them from falling all the way 

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Probotix FireBall V90 CNC Robot 

Step 11 — Secure tension rods 

• This part is a bit tricky. Fish around with the threaded rod, inside each pipe section, until 
you hit the hole in the lower base end. Once you find it, lower the threaded rod as far 
through it as you can. 

• Once you get each of the four tension rods through the right holes in both ends of the 
base, grasp the base assembly by the ends, applying pressure along its length to keep 
everything together, and rotate it into a horizontal position on your work surface. 

• Put a flat washer over the free end of each threaded rod, and secure it with a hex nut. 
Again: just finger-tight, at first. 

Step 12 — Install gantry 

• Set the gantry assembly in place on the gantry slides. 

• Put three machine screws through the three holes at each end of the gantry floor, passing 
them down through the three mating holes in each gantry slide. 

• Secure each gantry slide with three flat washers and three hex nuts, one for each screw. 
Go ahead and tighten them one turn past finger-tight. 

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Probotix FireBall V90 CNC Robot 

Step 13 — Adjust frame 

• Tighten each of the four long tension rods one turn past finger-tight, using a wrench on 
each end of each rod. 

• Adjust the tension on the four rods as necessary until the gantry slides smoothly on the 
rails from the pressure of one finger. 

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Probotix FireBall V90 CNC Robot 

Step 14 — Assemble long lead screw 

• Every V90 I've seen has the long horizontal-axis stepper motor mounted on the 
"tool side" of the gantry. If both of your base ends have motor mount holes, 
however, I haven't yet thought of any reason why you shouldn't mount the motor on the 
"back side" of the gantry. If you're not feeling adventurous, however, best to stick to the 
side pictured in the photo. 

• Pass the long lead screw through the bearing support hole in the base end on the same 
side that the motor will be mounted. 

• Once the lead screw is inside the frame, slip a bearing assembly, a nylon washer, and a 
shaft collar over its end, in that order. Note that the narrower diameter of the bearing 
assembly should be directed towards the bearing support hole. 

• Pass the lead screw into the lower drive nut assembly and thread it through the anti- 
backlash nut. 

• As before, threading the drive screw through the anti-backlash nut will cause a 
small cardboard retaining plug to be pushed out. Do not remove this plug in any 
other manner, and do not back the screw out once you've started it in. If the nut does fall 
apart, don't worry: It can be fixed. See this document for more info. 

• Once the lead screw is through the anti-backlash nut, slip the remaining shaft collar, nylon 
washer, and bearing assembly over its end, in that order. Again, make sure the bearing 
assembly is facing the right way. 


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Probotix FireBall V90 CNC Robot 

Step 15 — Secure long lead screw 

• Adjust the lead screw assembly, as before, such that about 3/4" of the brass coupling is 
exposed outside the base end. 

• Seat the bearing assemblies firmly in the base ends and butt the nylon washers and shaft 
collars close up against them. 

• Secure each shaft collar in place by tightening its set screw using a 7/64" Allen wrench. 

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Probotix FireBall V90 CNC Robot 

Step 16 — Install stepper motors 

• Note: Probotix officially recommends filing or grinding a small flat on the round 
motor shafts before installation to make it easier to remove them, later. I did not do 
so, and have not had cause to demount the motors yet, so I can't say one way or the 
other. But the machine does work fine, without grinding flats. 

• Mount both horizontal- and the single vertical-axis stepper motors by first inserting each 
motor shaft in the exposed brass coupling at the end of its corresponding lead screw. 

• Rotate each motor to align the four mounting holes in the motor case with those in the V90 

• Insert four screws through the mounting holes in each motor case, passing each through a 
flat washer and a nylon standoff (in that order) before starting the threads in the V90 

• Use a Phillips-head screwdriver to turn down the motor mounting screws securely. As 
always, do not overtighten. 

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Probotix FireBall V90 CNC Robot 

Step 17 — Secure motor couplings 

• Use a 3/32" Allen wrench to tighten the set screw in each of the three brass motor 
couplings against the motor shaft. 

Step 18 — Finishing touches 


• Put the spoilboard in place between the base ends, with the recessed ends of the mounting 
holes facing up. 

• Pass a 1/4-20 slotted-head machine screw through each of the spoilboard's four mounting 
holes, from top to bottom, and thread it into the corresponding T-nut on the underside of 
the table support bar. Turn down with a flathead screwdriver, but do not overtighten. 

• The V90 ships with a tool spindle designed to mount a Model 300 Dremel rotary 
tool. Mounts for other tools, including popular trim routers suitable for heavier work, 
are available through Probotix . 

• If you are using the Dremel tool holder, mount it to the vertical-axis assembly with the four 
bundled screws using a Phillips-head screwdriver. As always, do not overtighten. 

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Probotix FireBall V90 CNC Robot 

This guide covers construction of the mechanical system-the Cartesian robot-itself. To 
complete a working CNC machine around the V90 robot, you will need a means to generate G- 
code instructions, a suitable computer to run the control software, the control software itself, and 
the interface electronics. See Probotix' document, An Introduction to the FireBall V90 for more 

If you're building a V90, be sure to check out the official Probotix V90 assembly page and Alan 
Parekh's build over on Hacked Gadgets . 

This document was last generated on 2012-10-31 10:11:45 PM. 

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